Privacy policy

Last updated: 17 August 2026

Two separate things live under the bahntastic name: the Chrome extension ("bahntastic — data saver for train Wi-Fi") and the browsing service on this website (the surf box, i.e. addresses under /s/ and /hd/). They handle data very differently — which is why they are described separately here.

Controller

Renneberg Media UG (haftungsbeschränkt)
An den Pfühlen 15, 16348 Wandlitz, Germany
Further details: legal notice (Impressum)
E-mail: kontakt@renneberg-media.de

Part 1 · The Chrome extension

Almost nothing is transmitted

The extension works locally in your browser. It sends no data to third parties, and there is no account, no advertising and no analytics. Updates are delivered solely by the Chrome Web Store (Google) through the browser's normal extension mechanism. The single exception is the coarse-pixel preview — it is on by default for new installations, can be turned off at any time, and is described in the next section. With it switched off, nothing leaves your browser.

Coarse-pixel preview (on by default, can be turned off)

In data-saver mode, withheld images show a coarse-pixel thumbnail rendered by our browsing service instead of an empty placeholder. This means the addresses of those images (and thus, indirectly, which page you are visiting) are transmitted to bahntastic.de. Part 2 of this policy applies to those fetches: no logs, no cookies, nothing is stored. As of version 0.9.5 the preview is on by default for new installations; the popup says so right next to the switch ("Preview images are served via bahntastic.de"). To turn it off: set the images switch in the popup to "None" (or "HD"), or disable the coarse-pixel switch on the settings page — then, as before, nothing leaves your browser. If you update from an older version, your previous choice is kept: an update never turns the preview on without asking. Clicking an image still loads the original directly from the page you are visiting, not through us; exempt sites (such as mail.google.com) stay untouched even with the preview active.

What is stored locally in your browser

• Settings (chrome.storage.sync): the selected mode (off / data saver / emergency), the address of your local diet proxy and the scroll-depth toggle. Note: if you have enabled Chrome sync in your browser, Google synchronises these settings between your devices through your Google account — that is a feature of your browser which we have no access to.
• Per-domain interaction signals (chrome.storage.local, never leaves the device): the number of image clicks, the number of times you left emergency mode, optionally your maximum scroll depth, and the rule set derived from these ("load this image automatically from now on"). Only the domain is stored (e.g. example.org), never the full address of a page.

Deletion: the popup clears the signals of the current domain with one click; uninstalling the extension removes everything.

Permissions, honestly explained

• The content script runs on every page so it can replace images before they are downloaded. It does not read page content and transmits nothing.
• The tracker blocker uses a static rule list that ships with the extension (declarativeNetRequest) — the extension never sees your traffic; the browser applies the rules itself.
• The proxy permission is only used in emergency mode and points to a proxy running on your own machine (default 127.0.0.1:8899) — not to our servers.

Part 2 · The browsing service on bahntastic.de

What the service does

You enter a target address, our server fetches that page, throws the ballast overboard and returns a text skeleton with coarse-pixel images. To do that, we necessarily process:

• the target address you enter or click — it is used for the fetch and not stored permanently;
• your IP address — solely for the abuse brake (request limits per minute and per day). The counters live only in the server's memory, are never written to disk, and vanish on every restart;
• your language preference (Accept-Language header) — it is passed on to the target site so you get pages in your language.

What the service does not do

• No logs: neither the target addresses you visit nor the content of those pages is logged. The service writes nothing to disk.
• No cookies: the service sets no cookies and forwards none — in either direction. Login headers (Authorization) are stripped as well. That is why signing in through the service deliberately does not work.
• No sharing: there are no analytics tools, no ad networks and no data sharing with third parties. The only "sharing" is the fetch of the target page itself — there, our server appears with its own IP and the honest user agent bahntastic-proxy; the target site never sees your IP.

Honesty note: the service saves data, it does not anonymise. Your path to bahntastic.de remains as visible as any other website visit (to your internet provider, for instance), and the target site sees our server's IP instead of yours — we promise no concealment beyond that.

Legal bases

Processing the target address and your language preference: performance of the service you requested (Art. 6(1)(b) GDPR). Processing your IP address for the request limit: our legitimate interest in running the service free of abuse (Art. 6(1)(f) GDPR).

Visiting this website itself

The pages on bahntastic.de are static, with no cookies, no tracking pixels and no embedded third-party resources (even the fonts come from your system). There is no user tracking.

Your rights

Under the GDPR you have the rights to access, rectification, erasure, restriction, data portability and objection. Frankly: because we store practically nothing, the answer to an access request will usually be that we hold no data about you. Still, write to us any time at kontakt@renneberg-media.de. You may also lodge a complaint with a data protection supervisory authority.